BACKGROUND The aims of this study were to confirm the presence of OmpK35 and OmpK36 in extended-spectrum beta-lactamase-producing and nonextended-spectrum beta-lactamase-producing Klebsiella pneumoniae and to determine the relationship between porin expression and resistance to third-generation cephalosporins. METHODS Fifty-two K. pneumoniae isolates were obtained and analyzed for extended-sp...

To investigate the contribution of LamB in Klebsiella pneumoniae antimicrobial resistance, we determined the MICs of various antibiotics and the frequency of mutation to increased cefoxitin or meropenem resistance of the strains CSUB10S (expressing only OmpK36), CSUB10R (lacking OmpK35 and OmpK36), and their derived isogenic insertion-duplication mutants deficient in LamB. Expression of LamB wa...

Klebsiella pneumoniae porin genes were analyzed to detect mutations accounting for the porin deficiency observed in many beta-lactam-resistant strains. PCR and Southern blot analysis revealed the existence of a third porin gene in addition to the OmpK36 and OmpK35 porin genes previously described. This new porin gene was designated ompK37 and is present in all of the clinical isolates tested. T...

Carbapenem-resistant Klebsiella pneumoniae caused an outbreak in a hospital in Rome, Italy. The clinical isolates were tested by antimicrobial susceptibility testing, pulsed-field gel electrophoresis, multilocus sequence typing, plasmid typing, and β-lactamase identification. The OmpK35 and OmpK36 porins were analyzed by SDS-PAGE, and their genes were amplified and sequenced. Complementation ex...

Two porins, OmpK36 and OmpK35, have been described previously in Klebsiella pneumoniae, and they are homologous to the Escherichia coli porins OmpC and OmpF, respectively, at both the DNA and amino acid levels. Optimal resolution of the two K. pneumoniae porins by electrophoresis on polyacrylamide gels is not achieved using gel systems already described for E. coli and requires modifications of...

Klebsiella pneumoniae porin genes were analyzed to detect mutations accounting for the porin deficiency observed in many b-lactam-resistant strains. PCR and Southern blot analysis revealed the existence of a third porin gene in addition to the OmpK36 and OmpK35 porin genes previously described. This new porin gene was designated ompK37 and is present in all of the clinical isolates tested. The ...

This study was conducted to investigate the association between ompK36 variants and international high-risk clones in Klebsiella pneumoniae. Fifty-nine sequence types (STs) divided into four ompK36 allele groups (groups A to D) were identified among 185 K. pneumoniae isolates. The major high-risk clones (29 ST11, 13 ST15, 7 ST37 and 1 ST147 isolates) were assigned to group A, while 6 STs (15 ST...

OmpK35 from Klebsiella pneumoniae is the homologue of Escherichia coli OmpF porin. Expression of OmpK35 in K. pneumoniae strain CSUB10R (lacking both OmpK35 and OmpK36) decreased the MICs of cephalosporins and meropenem > or = 128-fold and decreased the MICs of imipenem, ciprofloxacin, and chloramphenicol > or = 8-fold. MIC reductions by OmpK35 were 4 times (cefepime), 8 times (cefotetan, cefot...

BACKGROUND & AIM The aim of this study was the detection of OqxAB efflux pumps, OmpK35 and OmpK36 porins among extended-spectrum-β-lactamase-producing Klebsiella pneumoniae isolates from Iran. MATERIALS AND METHODS This study was conducted with 83 K. pneumoniae isolates from two hospitals in Tehran, Iran. Antibiotic susceptibility tests were performed by Kirby-Bauer disc diffusion and Broth M...